I have a 2000 Jetta TDI and it has some issues starting.
Below 32F (somewhere around there) it starts no problem (with a few times warming up the glow plugs).
Above 40F it has a real hard time starting. It will crank but it won’t catch right away. Typically if I do it a good 3 times by then it will catch though there have been a few times when it hasn’t.
Any time that it doesn’t start I can boost it with another car and then it starts fine. I have had the battery replaced (with one that supposedly has a lot of cold cranking amps). So, I don’t believe it is the batter anymore.
My garage doesn’t know much about diesels and I have tried a couple of places, but they are all puzzled. Any ideas why it is hard to start when it is a little warmer out?
I had a '59 MB diesel when I got out of college and it left me stranded in Chicago. It turned out to be the starter. Have a good shop check it out.
Do you have the original timing belt? If it has been replaced, did this problem show up before or after? Have you had any CELs?
BTW you might want to stop by http://www.tdiclub.com/ as they have everything TDI.
Off hand my guess is a battery cable issue. Removing and cleaning each end of each battery cable might get you out of the problem. It also could be an internal failure in a battery cable.